Central Autonomous Nervous System Flashcards
What is the central nervous system?
Made up of the brain and the spinal cord.
The brain receives and processes sensory information, stores memories, initiates responses and generates thoughts and emotions.
The spinal cord conducts signals to and from the brain, and coordinates reflex activities.
What is the peripheral nervous system?
The nervous system outside of the brain and spinal cord. It conducts information to and from the central nervous system. It contains the cranial nerves and the spinal nerves.
It can be split into Efferent Motor neurones, and afferent sensory neurones.
Motor neurones can either be somatic (voluntary) or autonomic (involuntary).
Autonomic nerves can either be sympathetic (speed up/increase) or parasympathetic (slow down/decrease)
What is the autonomic nervous system?
Autonomic nervous system includes the sympathetic (fight or flight) and the parasympathetic system (rest and digest).
Can work independently but mainly work in synergy.
Functions to control involuntary physical processes.
Describe the parasympathetic nervous system
Rest and digest.
Helps to relax the body after times of stress, and carries out life maintaining functions when at rest, such as digestion, urination and lowering resting heart rate.
Describe the sympathetic nervous system
Fight or flight, activated in times of stress, danger or times of physical activity.
Includes raising heart rate and respiratory rate, increasing adrenaline, cause sweating, pupil dilation, decrease activity in the gut.
How is the autonomous nervous system organised overall, are there differences between parasympathetic and sympathetic?
All nerves are efferent - motor
Consists of 2 neurones that synapse at 1 ganglion.
Preganglionic neurones are myelinated and postganglionic neurones are non-myelinated.
Preganglionic neurones are shorter in sympathetic and longer in parasympathetic
2 transmitters are acetylcholine and noradrenaline
Acetylcholine = cholinergic
Noradrenaline = adrenergic
Where are Preganglionic neurones found for the parasympathetic nervous system? What is their course?
Cranial nerves from brainstem CN III, VII, IX, X
Also Sacral area of spine, s2-4
They travel to glanglia close or within the target organ.
Where are sympathetic Preganglionic neurones found?
Spinal segments T1-L2 - lateral horn
Travel to paravertebral and prevertebral ganglia
Paravertebral ganglia form the sympathetic chain, and extend from the base of the skull.
What is the course of a sympathetic Preganglionic neurone?
Leave ventral horn and then either:
- Travels down spinal nerve to prevertebral ganglion - Enters sympathetic trunk via grey ramus communicans ○ Then leaves via splanchic nerve ○ Travels up or down the trunk ○ Leaves to spinal nerve via grey ramus communicans
What is the the sympathetic trunk?
Nervous ganglia located either side of the vertebral column from the base of the skull to the coccyx. It allows nervous transmission to spinal nerves from one level of spinal column to another up and down the trunk.
Sympathetic nerves arise from the thoracolumbar region so must ascend to reach the cervical area.
Describe the cervical sympathetic trunk and what each ganglion innervates. What may sometimes be present / absent?
Spreads from c1-8
superior cervical ganglion= c1-4
- ICA and ECA
- viscera of head
middle = c5,6
- middle cardiac nerves
- viscera of neck upper thorax and upper limb
inferior = c7, 8
- vertebral artery
- viscera of neck, upper thorax and upper limb
- inferior cardiac nerves
Middle ganglion is sometimes absent.
In 80% of people, inferior ganglion fuses with first thoracic ganglion to form Stellate ganglion.
How is information processed in vertebrae?
Sensory information travels into the dorsal horn of the vertebrae after it is synapsed at the dorsal root ganglion. From here it is sent via ascending pathways to the brain to be processed.
The brain then sends sensory information to the lateral horn or the ventral horn. (Can be bypassed for a reflex movement and paths directly to ventral horn)
It then travels through the body of the vertebrae to the lateral horn (pelvic or visceral organs), or the ventral horn (skeletal muscle) where it is transmitted out to the spinal nerve where
What 4 ways can information leave the sympathetic trunk?
1- leave ventral root and synapse in sympathetic trunk via white ramus commincans, and ascend or descend to a different level.
2- leave ventral root and synapse with sympathetic trunk via WRC, then leave via their own nerve (splanchnic postganglionic nerve)
3 - leave ventral root and travel through WRC but do not synapse with sympathetic trunk, but travel down pre ganglionic splanchnic and synapse with a ganglion closer to target area
4 - leave ventral root and travel via WRC to sympathetic trunk, synapse, leave ST via grey ramus commincans and travel down spinal nerve on same level
Where are the cervical ganglion found in the head?
Just lateral to the spinal column at levels:
superior = C1/2
Middle = C6
Inferior = C7
What is horners syndrome and some clinical features?
It is damage to the sympathetic trunk resulting in a loss of sympathetic responses on the ipsilateral side of the head
Clinical features include:
- constricted pupil (miosis) due to unopposed parasympathetic innervation
- drooping of superior eyelid (ptosis) due to paralysis of smooth muscle component
- vasodilation and absence of sweating on face and neck (flushed face and anhydrosis) caused by lack of sympathetic vasoconstriction to blood supply and sweat glands
